Structural composite parts for aircrafts may be produced by mechanical forming or hot drape forming of a blank or stack of layers comprising pre-impregnated fibre plies (pre-preg tapes), each layer having fibres with a specific fibre direction. The stack is produced by laying up in a plane parallel with each other almost edge edge pre-fabricated pre-preg tapes. Between the edges often occurs a gap. The gap will be closed by the next layer laid upon the first layer. This means that longitudinal gaps in each pre-preg tape plane often occurs in the stack and which will weaken the finished structural composite part.
For example, a wing (aircraft structure) may comprise assembled upper and lower shells, beams, wing ribs (three-dimensional structural composite parts). An aileron (aircraft structure) may comprise assembled shell, conic formed beams, radius fillers (three-dimensional structural composite parts). These structural composite parts (with exception of the mentioned radius fillers) are formed of blanks comprising layers of said pre-preg tapes. The pre-preg tape is a pre-impregnated fibre ply having an elongated extension. The pre-preg tape comprises fibres (such as made of carbon, glas, ceramic, organic) which are oriented parallel with each other and extending in said elongated extension. The blank is thus built of a first layer of edge to edge positioned pre-preg tapes having the same fibre direction. A second layer of pre-preg tapes is applied onto the first layer but with a different fibre direction. The second layer also consists of edge edge positioned pre-preg tapes which have been laid up parallel to each other, the edges of two adjacent positioned being close to each other, either creating a gap or an overlap (wherein the excess portion of the pre-preg tape overlapping the other has to be removed before the next layer is applied). The definition of edge edge positioned pre-preg tapes means that the they are in position side by side, i.e. with their longitudinal side edges close to each other and the planes of the pre-preg tapes in one common plane. The pre-preg tapes can be fibre layers impregnated with resin before being placed on a temporary support by means of for example an Automatic Tape Laying-machine. The stack has thus fibre plies in each plane arranged onto each other, with different fibre directions, when comparing one plane with another. The stack is thereafter moved to a forming tool for forming the stack into the three-dimensional shape, or at least a two-dimensional shape. When forming the stack of plies over the forming tool, a force generated from a forming medium (e.g. vacuum bag or rollers) will generate shearing forces onto the stack of plies, wherein the plies (or planes) will slide against each other. This is achieved for avoiding wrinkles in the finished formed three-dimensional structural composite part. The benefit with the gliding effect or sliding between the plies is several, especially the lack of wrinkles. It is desirable to avoid wrinkles and at the same time achieve a reinforced structural composite part.
There is thus a need for a reinforced structural composite part including a number of layers of pre-preg tapes, each layer being composed of (in a common plane) side by side laid pre-preg tapes.
US 2008/0286564 A1 describes a method of building a composite structure having fibre layers in a stack, wherein carbon nanotubes are positioned between the layers for strengthening the stack constituting the composite part. The composite part is thus strengthened by applying the nanotubes between the main planes of the pre-preg tapes, i.e. between two layers, laid upon each other.
Furthermore, the document WO 2007/136755 describes a method of growing nanostructures. The nanostructures are used for building a stack of pre-preg ply layers.
Furthermore, the document WO 2008/115301 describes a composite laminate used in structural applications including a nanostructure interlayer of soft material that provides damping action to reduce noise and vibration.
There is thus a need for a further reinforced structural composite part comprising a first layer with parallel in a common plane applied pre-preg tapes side by side, onto which further a second layer with in a common plane parallel applied pre-preg tapes are arranged. Further is a next layer is positioned onto said second layer and so on. The number of layers also determines the strength. A large number of layers involves however a heavy structural composite part and there is a need to decrease the weight, still maintaining the strength.
Furthermore, there is a need for a cost-effective production of structural composite parts comprising layers of pre-preg plies, wherein the production time is shorter than that of producing prior art.
There is also a need for a cost-effective forming of a stack of pre-preg tapes being laid in layers.